The fall arrest industry worldwide manufactures and installs several types of overhead fall protection systems. They are used to prevent workers from injury or death due to falls from height.
Virtually all overhead fall arrest systems consist of a full body harness, worn by the user, which is secured to the anchorage by a lanyard. The lanyard can be cable or webbing and the harness is made of webbing to distribute the fall arrest loads on the body to prevent injury.
A variety of fall protection systems are available. There are single point anchors where the user is restricted to a 30 degree cone or envelope below the anchor point. There are also linear systems whereby the lanyard is attached to a trolley or shuttle which allows the user to traverse along while maintaining constant protection. One such linear system is the “safety cable” system. The cable-based system consists of one or more cables strung between two points. A cable trolley rides on the cable anchoring the lanyard, harness and user to the cable. Another type of fall protection system, in limited commercial use today, is the trolley beam, sometimes referred to as I-Beam style system. The typical I-beam style fall protection system includes an I-beam suspended above the structure to be traversed, a trolley which rides on the horizontal web of the I-beam, and a safety harness which is worn by the worker. The trolley in the I-beam system is typically a four-wheeled device that is designed to ride on the lower leg or flange of the horizontal web of the I-beam, and includes an attachment point (typically a carabiner) to secure the lifeline to the trolley.
Due to static loads and the loads placed on the I-beam when the lanyard engages during a fall event, the I-beam is prone to distorting. Cable systems can allow a user to fall further than desired before the lanyard engages due to dynamic deflection of the cable.
The trolleys on I-beam type systems are prone to hang-ups. For example, objects such as dust, dirt, snow, and ice are prone to collect on such systems resulting in an injury hazard when the object falls off the beam, particularly when struck by the trolley. In addition, such objects present a contamination hazard of the work areas below the I-beam system, particularly in the grain industry where, for example, food-grade grain is contained in open railcars below the system. Furthermore, a swing-fall hazard is created when the trolley hangs-up and remains far behind the user instead of directly overhead.